Acute lymphoblastic leukemia (ALL) is the most common childhood cancer, accounting for 25% of all childhood malignancies. Treatment of childhood ALL has a high success rate, with long-term event-free survival of >85%. Treatment success, however, has not come without cost. Recognition of long-term health problems related to childhood cancer therapies is growing. Both during and after therapy, children treated for ALL are at risk for fatigue, reduced physical activity, poor dietary intake, and excessive weight gain, which are driven by physiological (chemotherapy-induced) changes and social (home/environmental) factors. Specifically, chemotherapy-related inflammation and oxidative stress contribute to fatigue and weight gain, which are sustained by low levels of physical activity, poor dietary intake, and home environmental factors. Very few randomized controlled trials have been directed towards minimizing the negative impact of cancer treatment on body weight, diet, and activity levels in children after ALL. Previous studies have been predominantly center- based interventions, which are time consuming for families and difficult to replicate in standardized fashion across institutions, resulting in poor attendance and completion rates and small sample sizes. Moreover, most intervention studies have not paired physical activity with nutrition guidance and few have focused on young children. The goals of this pilot study are to evaluate the feasibility, acceptability, and potential efficacy of a parent-targeted, phone-delivered nutrition and physical activity program to prevent unhealthy weight gain among 60 childhood ALL survivors, 3-10 years of age. Unlike previous lifestyle-intervention studies among pediatric cancer survivors, our approach directly engages parents to modify home environmental factors related to physical activity and dietary intake to reduce fatigue, disrupt th cycle of inflammation and oxidative stress, and prevent unhealthy weight gain after chemotherapy. Intervention success in this pilot study will be benchmarked by changes in key weight-related behaviors (physical activity and dietary intake) over the 6- month trial, and initia impact of the intervention on biomarkers of inflammation and oxidative stress, fatigue, and body composition will be examined. The role of potential moderators of adherence, acceptability, and efficacy will also be explored (i.e., parenting stress, perceived child vulnerability). Findings frm this study will be used to inform a broader grant application to evaluate the efficacy of this intervention in a large-scale, multisite trial. As a first step, the proposed study would provide important scientific and practical information regarding the feasibility of delivering this intervention, the attractiveness of such programs to parents of childhood cancer survivors, and the potential effectiveness of the intervention for promoting healthy dietary intake, physical activity patterns and healthy weight, reducing fatigue, and improving biomarkers of inflammation and oxidative stress in children who have completed chemotherapy for ALL.